1. Field of the Invention
The present invention relates to the field of consumer electronic devices coupled in an audio/visual network. More specifically, the present invention pertains to a system and method for organizing and accessing data stored in a hard disk device in the audio/visual network.
2. Background Art
Audio/visual (AV) network architectures provide a powerful platform on which device functionality and interoperability can be built, and are capable of taking advantage of the increased sophistication that is being incorporated into consumer electronic devices. The typical AV home or office network consists of a variety of consumer electronic devices that present and record AV media in different ways. For instance, the typical AV equipment found in a home includes a number of components such as a radio receiver or tuner, a compact disk (CD) player and/or a digital video disc player (DVD), a number of speakers, a television, a video cassette recorder (VCR), a tape deck, and the like, and also may include a personal computer (PC).
A communication standard, the IEEE 1394 standard, has been defined for networking consumer electronic devices using a standard communication protocol layer (e.g., the audio visual control [AV/C] protocol). The IEEE 1394 standard is an international standard for implementing an inexpensive high-speed serial bus architecture for interconnecting digital devices, thereby providing universal input/output connection. The IEEE 1394 standard defines a digital interface for applications, thereby eliminating the need for an application to convert digital data to an analog form before it is transmitted across the bus. Correspondingly, a receiving application will receive digital data, not analog data, from the bus and will therefore not be required to convert analog data to digital form. The IEEE 1394 standard is ideal for consumer electronics communication in part because devices can be added to or removed from the serial bus while the bus is active. The IEEE 1394 standard supports both asynchronous and isochronous format data transfers.
Prior Art FIG. 1 illustrates an exemplary hard disk device (HDD) 10 commonly used for storing asynchronous and isochronous data. Data are stored on platter 6 that rotates on spindle 4. HDD 10 has a number of movable read/write heads 8 that are moved closer to or further from the center of platter 6 using arm 2 in order to read from or write to different parts of platter 6. A hard disk device typically has several platters stacked vertically and attached to spindle 4. In such a configuration, arm 2 will have one read/write head for each surface of the platters.
The radial position of the heads relative to spindle 4 is called the cylinder. Each head is wide enough to read or write from one track. Tracks are divided into sectors containing a certain number of bytes of data, typically 512 bytes. To access data on HDD 10, it is necessary to specify a cylinder and head, which together identify a specific track, the sector number where the data starts, and the number of bytes to be accessed. Data transactions generally start at the beginning of a sector.
In prior art computer systems, an object stored on HDD 10 is normally accessed by a logical block address. HDD 10, or the program controlling HDD 10, performs a limited amount of mapping to map the logical address for the object to the physical location of the associated data on the disk. The user is presented with what appears to be a contiguous range of logical blocks, providing the illusion that objects are stored contiguously on HDD 10 even though that is often not the case. This prior art method for storing data is problematic because it does not allow HDD 10 to be easily shared by multiple objects that do not work well together. For example, applications such as the Windows and Unix systems do not work well together on HDD 10 unless they are separated into partitions. However, the size of the partitions is difficult to change, and so the prior art is also problematic because it is not flexible and objects cannot be readily changed in size.
Another type of “track” is with regard to the sequence of the media stored in consumer minidisks (MDs). As new content is loaded into the MD it is stored at a track number. However, track numbers can change often over the course of time. For example, the deletion or insertion of file stored at a track affects all of the following tracks, shifting the number of a following track by one position. Hence, the track number cannot be used to address objects shared by multiple devices in the AV network because the track number may change between the time the object was recorded on the MD and the time it is later accessed and retrieved by another device on the network. A device on the network may store a certain track number that initially specifies a particular object, but at some later time when the device specifies that track number it very well could receive a different object than what is required. For example, an object initially identified on an MD as “track[3]” will be subsequently identified as “track[2]” if a file stored at a preceding track is deleted, and “track[4]” will then be known as “track[3].” A device on the AV network that then requests “track[3]” from the MD will receive the track previously identified as track[4] instead of the desired track.
Thus, there is currently a lack of mechanisms and methods for uniformly naming and organizing information (an “object”) stored on a HDD in an AV network, in particular a network compliant with the AV/C protocol, and for representing those objects to a user or to other devices in the AV network. Within an AV network in which many different types of devices may be coupled together, it is desirable to represent the objects in a uniform manner so that they can be readily accessed by a user or by other devices in the network.